HFPO, the epoxide product of the partial oxidation of HFP, is a highly reactive and versatile intermediate that can be converted to perfluoroalkylvinylethers. It is used in the production of proton-exchange members for fuel cells and to make heat-resistant fluids, high-temperature lubricants, high-performance elastomers and surfactants. Known non-catalytic epoxidation processes for the production of HFPO suffer from various problems such as the production of large quantities of environmentally unfavourable waste and/or high reagent costs due to the use of solvents and/or chemical oxidising agents such as hypohalites, hydrogen peroxide and organic peroxides, which can also be hazardous to operators. Moreover, with known non-catalytic batch processes which employ oxygen as the oxidising agent for the epoxidation of HFP, it is difficult to achieve adequate rates of production of HFPO. This invention seeks to ameliorate the abovementioned problems, at least to some extent, while achieving an adequate rate of production of HFPO i.e. a good selectivity towards HFPO at an acceptable yield.